Push button pulse signal generator

ABSTRACT

A pushbutton signal generator includes a coil mounted in a cylindrical housing with a plunger positioned in the center of the coil. The plunger is held in a fixed position by a permanent magnet within the housing. A push button may be depressed to drive the plunger through the coil thereby generating a pulse signal in the coil when the coil is placed in a circuit.

United States Patent [191 Britton et al.

[ 51 Feb. 27, 1973 [54] PUSH BUTTON PULSE SIGNAL GENERATOR [75]Inventors: Leon R. Britton, Chicago; Frank S. Vojir, Berwyn; William W.Wright, Wheaton, all of I11.

[73] Assignee: Guardian Electric Manufacturing Company, Chicago, Ill.

[22] Filed: Aug. 11, 1971 [21] Appl. No.2 170,729

[52] U.S. Cl. ..310/l5 [51] Int. Cl. ..H02k 35/06 [58] Field of Search..3l0/l5, 30,12-14 [56] References Cited UNITED STATES PATENTS 3,398,302Hamau et al. ..3l0/l5 X 3,132,268 5/1964 Abel et al. ..310/l5 3,130,3324/1964 Zehfeld et al. ....3l0/l5 3,l53,736 lO/l964 Etter ..310/l53,116,428 12/1963 Blodgett et al. ..3l0/l5 Primary Examiner-D. F. DugganAttorney-A. W. Molinare et al.

57 ABSTRACT A pushbutton signal generator includes a coil mounted in acylindrical housing with a plunger positioned in the center of the coil.The plunger is held in a fixed position by a permanent magnet within thehousing. A push button may be depressed to drive the plunger through thecoil thereby generating a pulse signal in the coil when the coil isplaced in a circuit.

4 Claims, 4 Drawing Figures PUSII BUTTON PULSE SIGNAL GENERATORBACKGROUND OF THE INVENTION In a principal aspect, the present inventionrelates to a push button pulse signal generator especially useful forproviding control signals in a circuit which includes the push buttonsignal generator.

Control circuits are often low voltage circuits. Therefore, a signalgenerator which provides a low voltage output, particularly a pulseoutput, can be easily integrated as part of a control circuit. Among thedesirable features of a signal generator for a control circuit aresimplicity of construction, low cost, ease of repair and reliability.Also, it is desirable to have as few moving parts as possible. Finally,it is desirable to have a signal generator which is compact or small.

A typical prior art switch is shown by U.S. Pat. No. 3,559,788 issuedFeb. 2, 1971 to Jensen et al. This patent discloses a switch whichprovides a signal by driving a permanent magnet through a coil. Themagnet is driven by moving a spring biased lever arm. It is desirable toeliminate mechanical parts of such a switch. The present invention, forexample, permits the elimination of the mechanical. spring from such aswitch.

SUMMARY OF THE INVENTION In a principal aspect, the present inventioncomprises an improved push button pulse signal generator wherein a coil,which is incorporated as part of the circuit, provides a pulse signaloutput whenever a plunger is driven through the coil by movement of apush button. The plunger is normally held in a fixed position by apermanent magnet. Depression of the push button overcomes the holdingforce of the permanent magnet on the plunger and permits the push buttonto drive the plunger through the coil thereby generating a pulse signalin the coil and the circuit.

It is thus an object of the present invention to provide an improvedpush button signal generator.

It is a further object of the present invention to provide an improvedpush button signal generator having no springs or contacts.

One further object of the present invention is to provide a push buttonsignal generator having a single moving part in addition to the pushbutton.

These and other objects, advantages and features of the invention willbe set forth in greater detail in the description which follows.

BRIEF DESCRIPTION OF THE DRAWING In the detailed description whichfollows, reference will be made to the drawing comprised of thefollowing FIGURES:

DESCRIPTION OF THE PREFERRED EMBODIMENT The apparatus of the inventionincludes a cylindrically shaped housing having an internal circum- FIG.1 is an exploded perspective view of the imferential flange 12 asillustrated in FIG. 1. A wire coil 16 having leads l8 and 19 is wound ona bobbin 14. The bobbin 14 is positioned against a lower surface 20 offlange 12. The bobbin 14 is maintained within the housing 10 by means ofan end cover or plate 22. Suitable openings in plate 22 permit the leads18 and 19 therethrough.

Anexternally threaded sleeve 24 is threaded into the opposite end of thehousing 10. Sleeve 24 maintains a metal keeper 26 and a permanent magnet28 in fixed position against an upper surface 30 of flange 12. Thekeeper 26 and permanent magnet 28 are therefore in a substantially fixedposition within the housing 10 and cooperate to maintain a plunger 32within the housing 10.

The unitary plunger 32 includes a flange 34 and a rod 36. Rod 36includes a lower portion 38 extending in one direction from the flange34 along the longitudinal axis of the housing 10. An upper portion 40 ofrod 36 extends in the opposite direction from flange 34. The lowerportion 38 extends into the center of coil 16. The upper portion 40extends through an annular opening 42 in the magnet 28 and is engaged bythe keeper plate 26 when the device is in an unoperated position. Thekeeper plate 26 also includes an opening 44. However, the opening 44 hasa smaller diameter than the diameter of the upper portion 40 in order tomaintain the plunger 32 in position by means of the keeper plate 26.

A push button 46 includes a rod shaped extension 48 extending throughthe opening 44 and in contact with the upper portion 40 of the rod 36.Flange surface 50 of the sleeve 24 and flange surface 52 of push button46 cooperate to maintain the push button 46 within the housing 10.

All of the components of the switch are cylindrically shaped andcoaxial. Thus, the push button 46, keeper plate 26, magnet 28, plunger32, coil 16, bobbin l4 and end plate 22 all have a common axis 55. Thehousing 10 and sleeve 24 have the same common axis. The button 46 andplunger 32 are translatable along the axis 55.

In operation, the plunger 32, which is fabricated from a materialattracted to a magnet, is maintained in position by the magnetic forceof the permanent magnet 28. In particular, the flange 34 is attracted bythe magnet 28. Thus, the plunger 32 is maintained in the position shownin FIG. 2. This simultaneously maintains the push button 46 in thenon-depressed position also shown in FIG. 2. I

To activate the signal generator, the push button 46 is manuallydepressed to overcome the force of the magnetic attraction of the magnet28 for the plunger 32. This drives the lower portion 38 of the plunger32 through the coil 16, thereby generating a pulse signal in a circuit.FIG. 3 illustrates the device subsequent to depression of the pushbutton 46.

Thus, the push button extension 48 impinges on the upper portion 40 ofthe plunger 32. When the manual force up on the push button 46 issufficiently great, the plunger 32 breaks away from the keeper plate 26quite suddenly, the lower portion 38 moving as suddenly through coil 16.This sudden breaking of the magnetic hold on plunger 32 and movement ofthe lower portion 38 in coil 16 causes a rapid change in the fluxdensity in the coil 16. in turn, a voltage is induced in the coil 16 anda connected circuit. Removal of the force upon the button 46 allows theplunger 32 to return under the influence of the permanent magnet 28causing a similar induced voltage, though of opposite polarity, in coil16. The plunger 32 thus returns to the position determined by the keeper26 and magnet 28.

The sudden breaking and remaking of the magnetic circuit between thekeeper 26 and plunger 32 provides the feel of a detent and springreturn. This feel as well as the output characteristics of the signalgenerator can be varied by changing the strength of the magnetic field,for example, (1) by using a magnet of different strength, or (2) bychanging the gap between the flange 34 and the magnet, or (3) bychanging the thickness or plating of the non-magnetic material onsurfaces of the keeper plate or plunger, or (4) by changing the materialand the gap between the flange 34 and the magnet 28. Additionally, theshape of the magnet 28, the shape of theplunger 32, or the constructionof the coil winding 16 can be varied to achieve differentcharacteristics of the signal.

FIG. 4 represents the typical variation in voltage with resistance of asignal generated by the generator of the present invention. Note thatsince the induced voltage in a circuit including the coil 16 is a resultin change of flux density in the coil winding, the return of the plunger32 into contact with the keeper plate 26 will also result in anotheroutput pulse signal having opposite polarity from the pulse signalcreated during depression of the push button 46. This may or may not bedesirable depending upon the design of the circuitry in which the deviceoperates. However, by proper use of a diode, the pulse signal of eitherpolarity can be blocked. I

Advantageously, the device has only one moving part, and it is not thetype or part which is required to flex such as a spring. Thus, thedevice has an exceptionally long life and simultaneously maintainsconsistent signal generating characteristics. Therefore, the apparatusof the present invention is to be limited only by the scope of thefollowing claims and their equivalents.

What is claimed is:

l. A push button signal generator comprising, in combination: a housinghaving a longitudinal axis and having mounted therein the following:

a. a coil with a center opening parallel to the longitudinal axis;

b. a plunger of magnetic material including a portion movable in thecoil opening, a flange portion outside one end of the coil and aprojection extending from said flange portion;

c. a magnet adjacent said flange portion for magnetically attractingsaid flange portion in a first direction;

d. a keeper plate for engaging said projection from said plunger tolimit the travel of said plunger in said first direction; and

e. push button means including an extension for engaging said plungerand driving said plunger in a direction opposite the first direction.

2. The signal generator of claim 1 wherein said coil is in a' circuit.

3. he apparatus of claim 1 wherein said keeper plate prevents physicalcontact of said flange and said magnet.

4. The apparatus of claim 1 wherein said flange is interrnediate saidcoil and said magnet.

1. A push button signal generator comprising, in combination: a housinghaving a longitudinal axis and having mounted therein the following: a.a coil with a center opening parallel to the longitudinal axis; b. aplunger of magnetic material including a portion movable in the coilopening, a flange portion outside one end of the coil and a projectionextending from said flange portion; c. a magnet adjacent said flangeportion for magnetically attracting said flange portion in a firstdirection; d. a keeper plate for engaging said projection from saidplunger to limit the travel of said plunger in said first direction; ande. push button means including an extension for engaging said plungerand driving said plunger in a direction opposite the first direction. 2.The signal generator of claim 1 wherein said coil is in a circuit. 3.The apparatus of claim 1 wherein said keeper plate prevents physicalcontact of said flange and said magnet.
 4. The apparatus of claim 1wherein said flange is intermediate said coil and said magnet.